JP3385996B2 - Diversity receiver - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diversity receiver and, more particularly, to a diversity receiver of a system for performing synthesis control based on waveform distortion after space diversity synthesis.

[0002]

2. Description of the Related Art FIG. 5 shows the structure of a conventional diversity receiver. In FIG. 5, only the part related to the diversity reception process in the diversity receiver is shown, and other configurations are omitted. The conventional diversity receiver has a frequency converter 101a which receives the input signal S1 as an input,
A frequency converter 101b having the input signal S2 as an input, an infinite phase shifter 102 connected to the frequency converter 101b, a combiner 103 connected to the output terminals of the frequency converters 101a and 101b, and a combiner 103 connected to the combiner 103. BPF (band pass filter) 104, automatic control amplifier 105 for amplifying the output signal of BPF 104, automatic control amplifier 105
Equalizer 400 and automatic control amplifier 1 connected to the output terminal of the
BPFs 401a and 401 connected in parallel to the output terminal of
b, 401c, the phase which outputs the tap coefficient for giving a phase rotation to the infinite phase shifter 102 based on the output signals of the detectors 402a, 402b, 402c and the detectors 402a-402c connected to the BPFs 401a-401c, respectively. It is configured to include a controller 403. A structure similar to this structure is described in JP-A-59-230333.

The frequency converters 101a and 101b convert the input radio frequency band signals (input signals S1 and S2) into intermediate frequency band signals. The infinite phase shifter 102 adjusts the phase of the reception signal supplied from the frequency converter 101b to 36.
It is rotated in the range of 0 ° and controlled to have the same phase as the received signal of the frequency converter 101a. The combiner 103 combines the received signals converted into the intermediate frequency band from the frequency converters 101a and 101b. The BPF 104 removes unnecessary signals outside the band. The automatic control amplifier 105 amplifies the level of the reception signal combined by the combiner 103 to a required value.

The BPFs 401a to 401c have a narrow band characteristic with respect to the signal band and are set so that their center frequencies are different from each other, and extract the signal components of each frequency band. The detectors 402a to 402c are the connection source BPF 40.
The output signals of 1a to 401c are detected, and the detected output is output to the phase controller 403. The phase controller 403 calculates the deviation within the signal band from each detection output value, and outputs a control signal to the phase shifter 102 so as to rotate the phase in the direction in which the deviation is minimized.

Next, the operation of the configuration shown in FIG. 5 will be described. The input signal S2 is converted into a signal in the intermediate frequency band by the frequency converter 101b and then input to the combiner 103. Further, the input signal S1 is converted into a signal in the intermediate frequency band by the frequency converter 101a, then directly input to the combiner 103, combined with the output signal of the infinite phase shifter 102, and output. This combined output is amplified to a required level by the automatic gain control amplifier 105 after the unnecessary component outside the band is removed by the BPF 104. Automatic control amplifier 105
The output signal of the equalizer 4 is input to the equalizer 400, and the equalizer 4
After the intersymbol interference wave included in the output signal of the automatic control amplifier 105 is removed by 00, the signal is output as an output signal.

The output signal of the whitening gain control amplifier 105 is
Further, it is input to the BPFs 401a to 401c. BPF
There are three types of BPFs having different center frequencies in order to extract the signal components on both sides of the center of the signal band of 104. The output signals of the BPFs 401a to 401c are detected by the detectors 402a to 402c at the connection sources.
As a result, the level of each signal component is detected. The detected signal level information is applied to the phase controller 403. The phase controller 403 calculates the level difference from the input signal level information of the three frequency components. The larger the level difference, the larger the waveform distortion in the signal band.
The state of this waveform distortion can be changed by rotating the phase of the output signal of the frequency converter 101b by the infinite phase shifter 102. Therefore, the phase controller 4
03 outputs phase rotation information, the infinite phase shifter 102 rotates the phase of the input signal S2 in accordance with this phase rotation information, and the phase controller 403 monitors changes in waveform distortion.
The phase controller 403 controls so that the waveform distortion is always minimized.

[0007]

However, according to the conventional diversity receiver, since the phase control is performed only from the information of the waveform distortion in the signal band, when the phase control is performed so as to follow the optimum phase, the combination is performed. Since the phase is controlled so that the level decreases, the line quality deteriorates due to the decrease in S / N.

Waveform distortion occurs due to multipath fading in the propagation path. Considering the two-wave model, in order to minimize the waveform distortion after combination, it is necessary to control the phase at the time of combination so that the main waves or echo waves of the two input received signals cancel each other. However, when the relationship between the relative phase and the relative level of the two-input main wave and the echo wave is close to each other, both the main wave and the echo wave cancel each other, and the level after synthesis decreases. This problem is also caused by the fact that the diversity synthesis control and the equalizer control are independent of each other, and therefore the diversity synthesis unit operates to equalize the waveform distortion more than necessary.

Further, according to the conventional diversity receiver, in order to detect the waveform distortion within the band, the BPF is set to 3 times.
It is necessary to provide a type. Therefore, there is a problem that the circuit configuration becomes complicated and the cost becomes high. Also, since these are usually composed of passive circuits in the intermediate frequency band,
It is necessary to consider variations in the BPF characteristics and the characteristics of the corresponding detectors, and the specifications become strict.

Therefore, an object of the present invention is to provide a diversity receiver which does not deteriorate the line quality at the time of diversity combining with a simple configuration.

[0011]

In order to achieve the above-mentioned object, the present invention converts each received signal by two antennas arranged with a predetermined distance to a predetermined frequency for each diversity path. , Second frequency converting means, phase shifting means for controlling the phase of the output signal of the second frequency converting means, and synthesizing means for synthesizing and outputting the output of the phase shifting means and the first input signal. And a decision feedback type equalizer for removing intersymbol interference waves included in the signal from the synthesizer, a relative output signal of the first frequency converter and an output signal of the second frequency converter. Phase difference detection means for detecting the phase difference, and phase control means for controlling the phase shift state of the phase shift means based on the relative phase difference detected by the phase difference detection means and the tap coefficient from the equalization means. Features To provide a diversity receiver.

According to this structure, the state of the waveform distortion after the combination by the combining means can be judged based on the information from the decision feedback type equalizing means and the phase difference information from the phase difference detecting means. Normally, in-phase synthesis control is executed, and when equalization by the equalizer is not possible (when waveform distortion by the non-minimum phase transition type occurs at the input of the equalizer), it tends to mitigate waveform distortion. Control the phase of the synthesizing means. As a result, the equalization capability of the decision feedback type equalization unit is maximized, and the phase control of the diversity combining unit functions so as to interpolate the equalization capability of the equalization unit. Therefore, it is possible to perform stable diversity combining control without deteriorating the line quality.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of the diversity receiver of the present invention. Here, only the portion related to the diversity reception processing in the diversity receiver is shown, and other configurations are omitted. The diversity receiver according to the present invention is connected to a frequency converter 101a (frequency conversion means) having an input signal S1 as an input, a frequency converter 101b (frequency conversion means) having an input signal S2 as an input, and a frequency converter 101b. Infinite phase shifter 102 (phase shift means), synthesizer 103 (synthesis means) connected to the output terminals of frequency converters 101a and 101b, this synthesizer 10
BPF 104 connected to No. 3, automatic control amplifier 105 for amplifying the output signal of BPF 104, automatic control amplifier 10
5 is connected to the output end of the decision feedback equalizer 106 (decision feedback equalizer), the frequency converter 101a, and the phase difference detector 113 (the phase difference detection) which receives the outputs of the infinite phase shifter 102. Means) and the infinite phase shifter 102 based on the output signals of the phase difference detector 113 and the decision feedback equalizer 106.
And a phase controller 112 (phase control means) that outputs a tap coefficient for applying a phase rotation to the.

The decision feedback equalizer 106 includes a front equalizer 107 connected to the automatic control amplifier 105, a combiner 108 connected to the front equalizer 107, and this combiner 108.
Inter-symbol interference included in the output signal of the automatic control amplifier 105, which is composed of a decision unit 109 connected to the decision unit 109, a rear equalizer 110 connected to the decision unit 109, and a subtractor 111 connected in parallel to the decision unit 109. Remove the waves. In the decision feedback equalizer 106, the front equalizer 107 equalizes the waveform distortion due to the non-minimum phase shift fading, and the rear equalizer 110 equalizes the waveform distortion due to the minimum phase shift fading. Since the front equalizer 107 is a linear equalizer, its equalization capability is weak, but the rear equalizer 110 is a non-linear equalizer, so its equalization capability is strong.

When the input signals S1 and S2 are input, the frequency converters 101a and 101b convert the radio frequency to the intermediate frequency for each path. Infinite phase shifter 1
02 controls the phase of the output signal of the frequency converter 101b. The combiner 103 combines the output signal of the infinite phase shifter 102 and the output signal of the frequency converter 101a. The phase difference detector 113 detects the relative phase difference at the input of the combiner 103. The BPF 104 attenuates unnecessary waves outside the band. The automatic control amplifier 105 amplifies the combined reception signal.

The phase controller 112 controls the amount of phase shift of the infinite phase shifter 102. This phase shift amount is normally controlled so that the output of the phase difference detector 113 is "0", that is, in-phase synthesis. When the tap coefficient of the forward equalizer 107 of the decision feedback equalizer 106 increases, the infinite phase shifter 102 is controlled so that the tap coefficient becomes the minimum.

FIG. 2 shows the detailed structure of the front equalizer 107. The forward equalizer 107 delays the signal from the automatic control amplifier 105 by n delay units 201-1 to 201-n, and complex delay units connected to the respective output units of the delay units 201-1 to 201-n. Multipliers 202-1 to 202-n, a transversal-equalization circuit unit including a combiner 203 connected to the output units of the complex multipliers 202-1 to 202-n, and a tap coefficient generator. It consists of 204. The tap coefficient generator 204 generates tap coefficients W1 to Wn to be given to the complex multipliers 202-1 to 202-n. Tap coefficient generator 20
4 is the output signal of the automatic control amplifier 105 and the subtracter 1
The tap coefficients W1 to Wn are generated based on the error signal from 11 (a signal indicating an error between the output signal of the combiner 108 and the signal required at the time of discrimination). Tap coefficient W1 to W
After n is converted from parallel data to serial data by the parallel / serial converter 205, it is output to the phase controller 112.

FIG. 3 shows the detailed configuration of the phase controller 112. The phase controller 112 is a switch 301 that receives the output signal (PH DET) of the phase difference detector 113 and the tap coefficients W1 to Wn, and determines the phase shift amount based on the phase control information selected by the switch 301. An arithmetic processing unit 302 (arithmetic processing unit) for calculating, and a sine wave generator 303 for outputting a tap coefficient for giving a phase rotation to the infinite phase shifter 102 based on the phase shift information output from the arithmetic processing unit 302.
(Sine wave generating means).

Next, the operation of the diversity receiver shown in FIG. 1 will be described. In a communication line using radio, a receiver having a diversity structure is used in order to improve S / N or mitigate waveform distortion due to fading of a propagation path. When there is little waveform distortion, frequency converter 1
In order to combine the reception signal from 01a and the reception signal from the infinite phase shifter 102, the phase difference detector 113 monitors the relative phase difference of the combiner 103. Frequency converter 101
The infinite phase shifter 102 is controlled so that there is no phase difference between the output signal of a and the output signal of the infinite phase shifter 102, that is, in phase. As a result, the signal components are added (combined) in phase and the S / N is improved. At this time,
Infinite phase shifter 102, combiner 103, phase difference detector 113
And the path of the phase controller 112 forms a feedback loop.

Next, when the waveform distortion cannot be ignored,
In-phase synthesis is not always optimal. That is, even if the in-phase condition is broken, the waveform distortion may be suppressed more by combining so as to cancel the main wave or the echo wave. Therefore, in order to detect the state of waveform distortion, the tap coefficients W1 to Wn of the front equalizer 107 are monitored by the phase controller 112.

4A and 4B show the relationship between the tap coefficients W1 to Wn and the tap coefficient amplitude value. FIG. 4A shows the state without waveform distortion, and FIG. 4B shows the case with large waveform distortion. The decision feedback equalizer 106 has a strong equalization capability with respect to the waveform distortion at the level at which the backward equalizer 110 operates, but the forward equalizer 1
The equalizing ability is weak with respect to the waveform distortion at the level at which 07 operates. Therefore, when the tap coefficient of the front equalizer 107 is equal to or less than the threshold value, the normal in-phase synthesis control is performed, and the decision feedback equalizer 106 equalizes the waveform distortion. On the other hand, when the values of the tap coefficients W1 to Wn exceed the threshold value, the frequency converter 1 minimizes the tap coefficients W1 to Wn.
The phase of 01b is controlled by the infinite phase shifter 102. In this case, a feedback loop is formed by the paths of the infinite phase shifter 102, the combiner 103, the forward equalizer 107, and the phase controller 112.

As described above, in the diversity receiver of the present invention, only when non-minimum phase shift type waveform distortion occurs at the input of the decision feedback equalizer 106,
The infinite phase shifter 102 is controlled so as to reduce this waveform distortion. That is, the waveform distortion that can be equalized by the equal decision feedback equalizer 106 is left as it is, and when the equalization cannot be performed by the decision feedback equalizer 106, it can be equalized by the decision feedback equalizer 106. Phase controller 11 so that the level of waveform distortion is reached
2 adjusts the phase of the infinite phase shifter 102. As a result, it is not necessary for the diversity combining unit to completely equalize the waveform distortion, and it is possible to avoid a situation in which the level of the combined signal decreases due to cancellation of both the main wave and the echo wave.

The output of the tap coefficient of the parallel / serial converter 205 of the front equalizer 107 is not limited to the serial output by the parallel / serial converter 205 of FIG. It is also possible to output in parallel.
Further, although the infinite phase shifter 102 controls the phase of the intermediate frequency, it is also possible to control the phase of the local signal given to the frequency converter 101b.

[0024]

As described above, according to the diversity receiver of the present invention, the phase shift control means detects the phase difference between two received signals, and based on this result and the information from the decision feedback equalization means. Since the amount of phase shift of the phase shift means is controlled by, it becomes possible to control the phase so that the level of the combined signal decreases, and it is possible to prevent the deterioration of the line quality due to the decrease of S / N. Further, since a plurality of narrow band BPFs and the same number of detectors that are conventionally required are not required,
It is possible to reduce the size and cost of the receiver.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a diversity receiver of the present invention.

FIG. 2 is a block diagram showing a detailed configuration of a front equalizer shown in FIG.

3 is a block diagram showing a detailed configuration of the phase controller of FIG.

FIG. 4 shows a relationship between tap coefficients W1 to Wn and tap coefficient amplitude values, (a) shows a state without waveform distortion, (b) shows
FIG. 4 is an explanatory diagram showing a case where waveform distortion is large.

FIG. 5 is a block diagram showing a configuration of a conventional diversity receiver.

[Explanation of symbols]

101a, 101b Frequency converter 102 infinite phase shifter 103 synthesizer 104 BPF (band pass filter) 105 Automatic gain control amplifier 106 Decision Feedback Equalizer 107 Forward equalizer 108 synthesizer 109 Judge 110 backward equalizer 111 subtractor 112 Phase controller 113 Phase difference detector 201-1 to 201-n delay device 202-1 to 202-n complex multiplier 203 synthesizer 204 tap coefficient generator 205 parallel / serial converter 301 Switch 302 arithmetic processing unit 303 Sine wave generator 401a, 401b, 401c BPF 402a, 402b, 402c Detector

Claims (4)

(57) [Claims] 1. A first and second frequency conversion means for converting respective reception signals from two antennas arranged at a predetermined distance into a predetermined frequency for each diversity path, and the second frequency conversion means. Phase-shifting means for controlling the phase of the output signal, the synthesizing means for synthesizing and outputting the output of the phase-shifting means and the first input signal, and the intersymbol interference wave included in the signal from the synthesizing means. Decision feedback type equalizing means for removing the phase difference, phase difference detecting means for detecting a relative phase difference between the output signal of the first frequency converting means and the output signal of the second frequency converting means, and the phase difference detecting means 2. A diversity receiver comprising phase control means for controlling the phase shift state of the phase shift means based on the relative phase difference detected in step 1 and the tap coefficient from the equalization means. 2. The phase control means, switching means for selecting and inputting either the tap coefficient from the equalizing means or the signal from the phase difference detecting means, and the selection content of the input by the switching means. Calculation processing means for calculating the phase shift amount for controlling the phase shift means, and sine wave generating means for converting the phase shift amount by the calculation processing means into a sine wave signal and outputting it to the phase shift means. The diversity receiver according to claim 1, further comprising: 3. The phase control means controls the phase shift means so that normal in-phase synthesis is performed when the tap coefficient from the equalization means is equal to or less than a threshold value, and the value of the tap coefficient is 2. The diversity receiver according to claim 1, wherein the phase shift means is controlled so that the tap coefficient becomes a minimum when the threshold value is exceeded. 4. The decision feedback type equalizer is a wave generated by non-minimum phase shift fading of a signal from the combiner.
Identifying a forward equalizer, a synthesizer and outputting the synthesized output signal of the forward equalizer and backward equalizer, and a signal required and the output signal of the synthesizer for equalizing the shape distortion Do
Determiner and an error of the previous SL combiner output signal and required by Ru signal the
Minute output as an error signal , and a minimum phase estimation of the output signal of the combiner via the determiner.
The backward equalization for equalizing waveform distortion due to transfer fading
The forward equalizer generates the tap coefficient based on the error signal from the subtractor to generate the non-minimum phase shift factor.
The touch performs equalization waveform distortion due Ejingu
Diversity receiver according to claim 1, wherein the kite includes a tap coefficient generator for delivering flop coefficients to said phase control means.